CN111525604A - Method and system for suppressing harmonic waves of flexible direct current transmission and computer equipment - Google Patents
Method and system for suppressing harmonic waves of flexible direct current transmission and computer equipment Download PDFInfo
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- CN111525604A CN111525604A CN202010453711.XA CN202010453711A CN111525604A CN 111525604 A CN111525604 A CN 111525604A CN 202010453711 A CN202010453711 A CN 202010453711A CN 111525604 A CN111525604 A CN 111525604A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Abstract
The embodiment of the invention relates to a method, a system and computer equipment for suppressing harmonic waves of flexible direct current transmission, wherein the method comprises the steps of obtaining three-phase alternating current output by a converter in the flexible direct current transmission and three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission; harmonic current control processing is carried out on three-phase alternating current and alternating voltage to generate three-phase harmonic modulation waves; inputting three-phase harmonic modulation waves into a converter valve control system of the flexible direct-current transmission, so that a converter in the flexible direct-current transmission outputs three-phase additional harmonic alternating-current voltages; the three-phase additional harmonic alternating voltage is input into the flexible direct current transmission, the three-phase harmonic alternating voltage at the grid-connected point of the converter in the flexible direct current transmission can be offset at any time, the harmonic current output by the converter in the flexible direct current transmission is 0, the harmonic current in the output current of the flexible direct current transmission is restrained, and the stability and the safety of the operation of the flexible direct current transmission are improved.
Description
Technical Field
The invention relates to the technical field of flexible direct current transmission, in particular to a method and a system for suppressing harmonic waves of flexible direct current transmission and computer equipment.
Background
The flexible direct current transmission is a novel transmission technology based on a voltage source converter, a self-turn-off device and a Pulse Width Modulation (PWM) technology, compared with the traditional direct current transmission technology, the flexible direct current transmission technology has the advantages of being capable of supplying power to a passive network, avoiding phase change failure, being easy to form a multi-terminal direct current system and the like, is also used for supplying power in a wind power plant grid, asynchronous networking and city, improving traditional direct current operation characteristics and the like, shows huge economic and technical advantages in application occasions, is an important technical basis for building a direct current power grid and developing an energy internet in the future, and is one of important development directions in the field of power transmission in the future.
The current control strategy design of the existing flexible direct current transmission usually focuses on the dynamic performance and the fault ride-through performance of a direct current transmission power grid under the condition of no distortion of the voltage of the power grid, and a special control strategy is rarely designed under the condition of voltage distortion of the direct current transmission power grid.
With the wide application of nonlinear loads such as high-capacity power electronics, the voltage distortion of a direct-current transmission power grid is increasingly serious, the influence caused by various harmonic disturbances in flexible direct-current transmission is increasingly prominent, and the harmonic frequency range is gradually enlarged. The influence of the existence of harmonic waves on the flexible direct current transmission comprises two types, wherein the first type is that a direct current system and an alternating current system in the flexible direct current transmission generate resonance interaction to cause harmonic amplification; the second type is that after the power grid of the direct current transmission power grid is distorted, the control link of the flexible direct current transmission does not have good inhibition effect on harmonic components in the flexible direct current transmission power grid, so that relatively obvious harmonic waves exist in output current, and the safe operation of the flexible direct current transmission is influenced. The flexible direct current transmission system optimizes and solves the first kind of influence by mature technology through control strategies and parameters, but no technology solves the harmonic waves in the second kind of influence at present.
Disclosure of Invention
The embodiment of the invention provides a method, a system and computer equipment for suppressing harmonic waves of flexible direct current transmission, which are used for solving the technical problem that the current output by the flexible direct current transmission contains harmonic waves and the safe operation of the flexible direct current transmission is influenced because harmonic components contained in the control link of the conventional flexible direct current transmission are not suppressed.
In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:
a method for suppressing flexible direct current transmission harmonic waves comprises the following steps:
acquiring three-phase alternating current output by a converter in flexible direct current transmission and three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission;
harmonic current control processing is carried out on the three-phase alternating current and the three-phase alternating voltage to generate three-phase harmonic modulation waves;
inputting the three-phase harmonic modulation waves into a converter valve control system of the flexible direct-current power transmission, and outputting three-phase additional harmonic alternating-current voltage by a converter in the flexible direct-current power transmission;
and inputting the three-phase additional harmonic alternating-current voltage into the flexible direct-current transmission, wherein the harmonic current output in the flexible direct-current transmission is 0.
Preferably, the method for suppressing the harmonic waves in the flexible direct current transmission further includes a harmonic current control formed by connecting m harmonic suppression links in parallel, each harmonic suppression link includes n to k harmonics, where m is n.
Preferably, the step of generating a harmonic modulation wave of three phases using the harmonic current control includes:
carrying out abc/dq coordinate transformation of m-order harmonic waves on the three-phase alternating current to obtain d-axis current and q-axis current under dq coordinates;
after the d-axis current and the q-axis current are subjected to low-pass filtering, a d-axis current direct-current component and a q-axis current direct-current component are obtained;
subtracting the d-axis current direct current component from a set d-axis current instruction value to obtain a d-axis current error, and subtracting the q-axis current direct current component from a set q-axis current instruction value to obtain a q-axis current error;
processing the d-axis current error and the q-axis current error by adopting a controller to obtain d-axis harmonic modulation voltage and q-axis harmonic modulation voltage;
carrying out dq/abc coordinate transformation on m-order harmonic waves on the d-axis harmonic wave modulation voltage and the q-axis harmonic wave modulation voltage to obtain harmonic wave modulation voltages of all phases under abc coordinates;
and summing the harmonic modulation voltages of each phase n to k, and then obtaining the harmonic modulation wave of each phase through an amplitude limiting link.
Preferably, the harmonic suppression method for the flexible direct current transmission further comprises an enabling controller for controlling the modulated wave to be input into or output from the flexible direct current transmission, and the enabling controller is arranged between summing and limiting the harmonic modulated voltage of each phase n-k.
Preferably, the controller is a proportional-integral PI controller.
Preferably, the controller is a proportional resonant PR controller.
Preferably, the method for suppressing the harmonic waves in the flexible direct current transmission further comprises the step of independently controlling each harmonic wave in a harmonic suppression link by using the harmonic modulation voltage of each phase.
Preferably, the additional harmonic ac voltage of each phase is input to the flexible dc power transmission, and the flexible dc power transmission outputs a harmonic current of each phase current of 0.
The invention also provides a suppression system of the flexible direct current transmission harmonic wave, which comprises a data acquisition unit, a processing unit, a conveying unit and a suppression unit;
the data acquisition unit is used for acquiring three-phase alternating current output by the converter in the flexible direct current transmission and three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission;
the processing unit is used for carrying out harmonic current control processing on the three-phase alternating current and the three-phase alternating voltage to generate three-phase harmonic modulation waves;
the transmission unit is used for inputting the three-phase harmonic modulation waves into a converter valve control system of the flexible direct-current transmission, and the converter outputs three-phase additional harmonic alternating-current voltages in the flexible direct-current transmission;
and the suppression unit is used for inputting the three-phase additional harmonic alternating-current voltage into the flexible direct-current transmission, and the harmonic current output in the flexible direct-current transmission is 0.
The invention also provides computer equipment, which comprises a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the method for suppressing the flexible direct current transmission harmonic according to instructions in the program code.
According to the technical scheme, the embodiment of the invention has the following advantages:
1. the method for suppressing the harmonic wave of the flexible direct current transmission generates a three-phase harmonic wave modulation wave by obtaining the three-phase alternating current output by the converter in the flexible direct current transmission, the three-phase alternating current voltage of the grid-connected point of the converter in the flexible direct current transmission and the three-phase alternating current voltage of the grid-connected point of the converter in the flexible direct current transmission through harmonic current control processing, the three-phase harmonic wave modulation wave outputs a three-phase additional harmonic wave alternating voltage through the converter valve control system in the flexible direct current transmission, the three-phase additional harmonic wave alternating voltage can offset the three-phase harmonic wave alternating voltage at the grid-connected point of the converter at any time, the harmonic wave current output by the converter is 0, thereby achieving the purposes of suppressing the harmonic wave current in the output current of the flexible direct current transmission, improving the stability and the safety of the flexible, the current output by the flexible direct current transmission contains harmonic waves, and the safe operation of the flexible direct current transmission is influenced;
2. the harmonic suppression system for the flexible direct current transmission acquires three-phase alternating current output by a converter in the flexible direct current transmission, three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission and three-phase alternating voltage of the grid-connected point through a data acquisition unit, a processing unit controls and processes the three-phase alternating current and the three-phase alternating voltage by harmonic current to generate three-phase harmonic modulation waves, a transmission unit inputs the three-phase harmonic modulation waves into a converter valve control system in the flexible direct current transmission to enable the converter to output three-phase additional harmonic alternating voltage, and the suppression unit is put into the flexible direct current transmission through the three-phase additional harmonic alternating voltage to enable the harmonic current output by the converter in the flexible direct current transmission to be 0, so that the harmonic current in the output current of the flexible direct current transmission is suppressed, and the stability and the safety, the technical problem that the current output by the flexible direct current power transmission contains harmonic waves and the safe operation of the flexible direct current power transmission is influenced because harmonic components contained in the control link of the existing flexible direct current power transmission are not restrained is solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is a flowchart illustrating steps of a method for suppressing a harmonic in flexible dc transmission according to an embodiment of the present invention.
Fig. 2 is an equivalent circuit diagram of a converter under the modulation wave of the method for suppressing the harmonic wave of the flexible direct-current transmission according to the embodiment of the present invention.
Fig. 3 is a flowchart of steps of harmonic current control in the method for suppressing a harmonic in flexible direct current transmission according to an embodiment of the present invention.
Fig. 4 is a frame diagram of a method for suppressing a harmonic in flexible dc transmission according to an embodiment of the present invention, in which a PI controller is used for controlling a harmonic current.
Fig. 5 is a block diagram of harmonic current control of a PR controller in the method for suppressing the flexible dc transmission harmonic according to the embodiment of the present invention.
Fig. 6 is a block diagram of a system for suppressing a harmonic in flexible dc transmission according to an embodiment of the present invention.
Detailed Description
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the present embodiment, the explanation of terms:
the flexible Direct Current Transmission is High Voltage Direct Current Transmission (VSC-HVDC) based on a Voltage Source converter, is a novel Transmission technology based on the Voltage Source converter, a self-turn-off device and a Pulse Width Modulation (PWM) technology, and has the advantages of being capable of supplying power to a passive network, avoiding phase change failure, avoiding communication among converter stations, being easy to form a multi-terminal Direct Current system and the like.
The embodiment of the application provides a method and a system for suppressing harmonic waves of flexible direct current transmission and computer equipment, and aims to solve the technical problem that the current output by the flexible direct current transmission contains harmonic waves and the safe operation of the flexible direct current transmission is influenced because harmonic components contained in the control link of the conventional flexible direct current transmission are not suppressed.
The first embodiment is as follows:
fig. 1 is a flowchart illustrating steps of a method for suppressing a harmonic in flexible dc transmission according to an embodiment of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a method for suppressing a harmonic in flexible direct current transmission, including the following steps:
s1, obtaining three-phase alternating current output by a converter in flexible direct current transmission and three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission;
s2, carrying out harmonic current control processing on three-phase alternating current and alternating voltage to generate three-phase harmonic modulation waves;
s3, inputting three-phase harmonic modulation waves into a converter valve control system of the flexible direct-current power transmission, wherein the converter outputs three-phase additional harmonic alternating-current voltages in the flexible direct-current power transmission;
and S4, three-phase additional harmonic alternating-current voltage is input into the flexible direct-current power transmission, and the harmonic current output in the flexible direct-current power transmission is 0.
In S1 to S4 of the present embodiment, the three-phase ac current i output from the inverter in the flexible dc power transmission is collecteda，ib，icGenerating three-phase harmonic modulation wave under abc coordinate through harmonic current control
Harmonic current control to generate three-phase harmonic modulated wave
Converter valve control system in flexible direct current transmission enables converter to output three-phase additional harmonic alternating current voltage
Additional harmonic AC voltage of the three phases
Three-phase alternating current harmonic voltage output by the converter can be offset from the converter at any momentAnd the three-phase harmonic alternating-current voltage at the grid-connected point enables the harmonic current output by the converter to be 0, and the suppression of the harmonic current in the output current of the flexible direct-current transmission is achieved. According to the method for suppressing the harmonic waves in the flexible direct current transmission, the harmonic waves in the current can be suppressed by modifying the parameters of the trigger pulses of the control converter, additional equipment does not need to be configured, and the cost is saved.
Fig. 2 is an equivalent circuit diagram of a converter under the modulation wave of the method for suppressing the harmonic wave of the flexible direct-current transmission according to the embodiment of the present invention.
Note that, as shown in FIG. 2, ush(i.e. harmonic modulated wave)
The voltage of the harmonic modulated wave of one phase) is the harmonic component of the voltage of the flexible direct current transmission network if uchIn order to equivalently output harmonic components after modulation of the flexible direct current transmission converter during control without harmonic suppression, the harmonic current control link of the invention is adopted to generate a dynamic additional voltage u 'by taking harmonic current as a control target'ch(i.e. additional harmonic AC voltage)
Voltage of one phase) which makes a harmonic current of an inverter output current in the flexible direct current transmission 0 in the flexible direct current transmission.
The method for suppressing harmonic wave of flexible direct current transmission provided by the invention generates three-phase harmonic wave modulation wave by obtaining three-phase alternating current output by a converter in the flexible direct current transmission, three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission and three-phase alternating voltage of the grid-connected point through harmonic current control processing, and enables the converter to output a three-phase additional harmonic wave alternating voltage through a converter valve control system in the flexible direct current transmission, the three-phase additional harmonic wave alternating voltage can enable the three-phase alternating harmonic wave voltage output by the converter to offset the three-phase harmonic wave alternating voltage at the grid-connected point of the converter at any moment, so that the harmonic wave current output by the converter is 0, thereby achieving the purposes of suppressing the harmonic wave current in the output current of the flexible direct current transmission, improving the stability and the safety of the flexible direct current transmission, and solving the problem that the harmonic wave component, the current output by the flexible direct current transmission contains harmonic waves, and the safe operation of the flexible direct current transmission is influenced.
Fig. 3 is a flowchart of steps of harmonic current control in the method for suppressing a harmonic in flexible direct current transmission according to an embodiment of the present invention.
As shown in fig. 3, in an embodiment of the present invention, the method for suppressing flexible direct current transmission harmonics further includes a harmonic current control formed by connecting m harmonic suppression links in parallel, where each harmonic suppression link includes harmonics of n to k orders, where m is n. The step of generating a three-phase harmonic modulated wave using harmonic current control includes:
s21, carrying out abc/dq coordinate transformation on m-order harmonic waves of three-phase alternating current to obtain d-axis current and q-axis current under dq coordinates;
s22, performing low-pass filtering on the d-axis current and the q-axis current to obtain a d-axis current direct-current component and a q-axis current direct-current component;
s23, subtracting the set d-axis current instruction value from the d-axis current direct component to obtain a d-axis current error, and subtracting the set q-axis current instruction value from the q-axis current direct component to obtain a q-axis current error;
s24, processing the d-axis current error and the q-axis current error by using a controller to obtain d-axis harmonic modulation voltage and q-axis harmonic modulation voltage;
s25, carrying out dq/abc coordinate transformation on m-order harmonic waves on the d-axis harmonic wave modulation voltage and the q-axis harmonic wave modulation voltage to obtain harmonic wave modulation voltages of all phases under abc coordinates;
and S26, summing the harmonic modulation voltages of each phase from n to k, and obtaining the harmonic modulation wave of each phase through an amplitude limiting link.
In S24 of the present embodiment, the method for suppressing harmonics in flexible direct current power transmission further includes an enable controller for controlling the modulated wave to be input into or output from the flexible direct current power transmission, and the enable controller is disposed between summing and limiting the harmonic modulated voltages of the phases n to k.
If the enable controller is set to 0, the three-phase harmonic modulation wave exits from a converter valve control system of the flexible direct-current power transmission; if the enable controller is set to be 1, the three-phase harmonic modulation wave is input into a converter valve control system of the flexible direct current transmission, the harmonic current output by the converter is made to be 0, and therefore the purpose of suppressing the harmonic current in the output current of the flexible direct current transmission is achieved. In the embodiment of the invention, the suppression method of the flexible direct current transmission harmonic wave can control the suppression of the harmonic wave by independently setting the enable controller to be 0 or 1, so that the input and exit of additional harmonic wave alternating current voltage are facilitated, and the suppression method is convenient and fast to use.
In S25 of this embodiment, the method for suppressing a harmonic in flexible direct current transmission further includes independently controlling each harmonic in the harmonic suppression link by using the harmonic modulation voltage of each phase, so that the method for suppressing a harmonic in flexible direct current transmission can control a plurality of harmonics with different frequencies at the same time, and a harmonic current in a current output by flexible direct current transmission is 0.
In S26 of the present embodiment, the clipping element limits the value of the harmonic modulation voltage after summation to a given upper limit value and lower limit value.
Fig. 4 is a frame diagram of a method for suppressing a harmonic in flexible dc transmission according to an embodiment of the present invention, in which a PI controller is used for controlling a harmonic current.
As shown in fig. 4, the harmonic current control adopts a proportional-integral PI controller, specifically: the three-phase alternating current i is collected in each harmonic suppression linka，ib，icAnd performing positive (negative) transformation on m-order harmonic abc/dq coordinates, wherein m is ndhmAnd q-axis current iqhmN, k, passing through a low-pass filtering element GfhTo obtain d-axis current DC component idhm1And q-axis current DC component iqhm1N, k, followed by d-axis dc component idhm1And q-axis current DC component iqhm1Respectively corresponding to the d-axis current command value
And q-axis current command value
And obtaining d-axis current error by taking the difference of m, n and k
And q-axis current error
N, k; d-axis current error
And q-axis current error
Through proportional-integral controller GPIObtaining d-axis harmonic modulation voltage
And q-axis harmonic modulation voltage
N, k. And (3) obtaining the abc three-phase m-order harmonic modulation voltage through positive (negative) inverse transformation of m-order harmonic dq/abc coordinates, wherein m is n
Harmonic modulation voltage of order m ═ n
The total harmonic modulation wave of the abc three phases is obtained after summing, enabling the controller Ken and amplitude limiting
In this embodiment, the enable controller Ken may be manually set to 0 and 1, the harmonic suppression function of the suppression method of the hvdc transmission harmonic exiting the hvdc transmission when set to 0, the harmonic suppression function of the suppression method of the hvdc transmission harmonic when set to 1The wave suppression function is put into flexible direct current transmission.
Fig. 5 is a block diagram of harmonic current control of a PR controller in the method for suppressing the flexible dc transmission harmonic according to the embodiment of the present invention.
As shown in fig. 5, the PR controller using proportional resonance for harmonic current control specifically includes: the three-phase alternating current i is collected in each harmonic suppression linka，ib，icAnd performing positive (negative) transformation on m-order harmonic abc/dq coordinates, wherein m is ndhmAnd q-axis current iqhmN, k, passing through a low-pass filtering element GfhTo obtain d-axis current DC component idhm1And q-axis current DC component iqhm1N, k, followed by d-axis dc component idhm1And q-axis current DC component iqhm1Respectively corresponding to the d-axis current command value
And q-axis current command value
And obtaining d-axis current error by taking the difference of m, n and k
And q-axis current error
N, k; d-axis current error
And q-axis current error
Through a proportional resonant controller GPRObtaining d-axis harmonic modulation voltage
And q-axis harmonic modulation voltage
N, k. And (3) obtaining the abc three-phase m-order harmonic modulation voltage through positive (negative) inverse transformation of m-order harmonic dq/abc coordinates, wherein m is n
Harmonic modulation voltage of order m ═ n
Through summation
m＝n，...，k、
m＝n，...，k、
N, k, enabling the controller Ken and obtaining the abc three-phase total harmonic modulation wave after amplitude limiting
In the present embodiment, the enable controller Ken may be manually set to 0 and 1, the harmonic suppression function of the suppression method of the hvdc transmission harmonic exits the hvdc transmission when set to 0, and the harmonic suppression function of the suppression method of the hvdc transmission harmonic drops into the hvdc transmission when set to 1.
Example two:
fig. 6 is a block diagram of a system for suppressing a harmonic in flexible dc transmission according to an embodiment of the present invention.
As shown in fig. 6, an embodiment of the present invention further provides a suppression system for flexible direct current transmission harmonics, including a data acquisition unit 10, a processing unit 20, a conveying unit 30, and a suppression unit 40:
a data obtaining unit 10, configured to obtain a three-phase ac current output by a converter in the flexible dc power transmission and a three-phase ac voltage at a grid-connected point of the converter in the flexible dc power transmission;
a processing unit 20, configured to perform harmonic current control processing on three-phase ac current and ac voltage to generate three-phase harmonic modulation waves;
a transmission unit 30 configured to input a three-phase harmonic modulation wave into a converter valve control system for the flexible dc power transmission, where the converter outputs three-phase additional harmonic ac voltages;
and a suppression unit 40 for inputting the three-phase additional harmonic ac voltage into the flexible dc power transmission, wherein the harmonic current output by the flexible dc power transmission is 0.
It should be noted that, the units in the system of the second embodiment are correspondingly arranged in the steps in the method of the first embodiment, and the details of the steps are described in detail in the method of the first embodiment, so that the details of the units in the system of the second embodiment are not described herein.
The invention provides a harmonic suppression system for flexible direct current transmission, which obtains three-phase alternating current output by a converter in the flexible direct current transmission, three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission and three-phase alternating voltage of the grid-connected point through a data acquisition unit, a processing unit controls and processes the three-phase alternating current and the three-phase alternating voltage by harmonic current to generate three-phase harmonic modulation waves, a transmission unit inputs the three-phase harmonic modulation waves into a converter valve control system in the flexible direct current transmission to enable the converter to output a three-phase additional harmonic alternating voltage, the suppression unit is put into the flexible direct current transmission through the three-phase additional harmonic alternating voltage to enable the harmonic current output by the converter in the flexible direct current transmission to be 0, thereby achieving the purposes of suppressing the harmonic current in the output current of the flexible direct current transmission and improving the stability and the, the technical problem that the current output by the flexible direct current power transmission contains harmonic waves and the safe operation of the flexible direct current power transmission is influenced because harmonic components contained in the control link of the existing flexible direct current power transmission are not restrained is solved.
Example three:
the embodiment of the invention provides computer equipment, which comprises a processor and a memory;
a memory for storing the program code and transmitting the program code to the processor;
and the processor is used for executing the method for suppressing the flexible direct current transmission harmonic wave according to the instructions in the program codes.
It should be noted that the processor is configured to execute the steps in the above-mentioned embodiment of the method for suppressing the hvdc transmission harmonic according to the instructions in the program code. Alternatively, the processor, when executing the computer program, implements the functions of the modules/units in the system/apparatus embodiments described above, such as the functions of the units 10 to 40 shown in fig. 6.
Illustratively, a computer program may be partitioned into one or more modules/units, which are stored in a memory and executed by a processor to accomplish the present application. One or more modules/units may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution of a computer program in a terminal device.
The terminal device may be a desktop computer, a notebook, a palm computer, a cloud server, or other computing devices. The terminal device may include, but is not limited to, a processor, a memory. Those skilled in the art will appreciate that the terminal device is not limited and may include more or fewer components than those shown, or some components may be combined, or different components, e.g., the terminal device may also include input output devices, network access devices, buses, etc.
The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The storage may be an internal storage unit of the terminal device, such as a hard disk or a memory of the terminal device. The memory may also be an external storage device of the terminal device, such as a plug-in hard disk, a Smart Memory Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like provided on the terminal device. Further, the memory may also include both an internal storage unit of the terminal device and an external storage device. The memory is used for storing computer programs and other programs and data required by the terminal device. The memory may also be used to temporarily store data that has been output or is to be output.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for suppressing harmonic waves in flexible direct current transmission is characterized by comprising the following steps:
acquiring three-phase alternating current output by a converter in flexible direct current transmission and three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission;
harmonic current control processing is carried out on the three-phase alternating current and the three-phase alternating voltage to generate three-phase harmonic modulation waves;
inputting the three-phase harmonic modulation waves into a converter valve control system of the flexible direct-current power transmission, and outputting three-phase additional harmonic alternating-current voltage by a converter in the flexible direct-current power transmission;
and inputting the three-phase additional harmonic alternating-current voltage into the flexible direct-current transmission, wherein the harmonic current output in the flexible direct-current transmission is 0.
2. The method for suppressing the flexible direct current transmission harmonic wave according to claim 1, further comprising a harmonic current control formed by connecting m harmonic suppression links in parallel, wherein each harmonic suppression link includes n to k harmonics, and m is n.
3. The method for suppressing a harmonic in a flexible direct current transmission according to claim 2, wherein the step of generating a harmonic modulated wave of three phases using the harmonic current control includes:
carrying out abc/dq coordinate transformation of m-order harmonic waves on the three-phase alternating current to obtain d-axis current and q-axis current under dq coordinates;
after the d-axis current and the q-axis current are subjected to low-pass filtering, a d-axis current direct-current component and a q-axis current direct-current component are obtained;
subtracting the d-axis current direct current component from a set d-axis current instruction value to obtain a d-axis current error, and subtracting the q-axis current direct current component from a set q-axis current instruction value to obtain a q-axis current error;
processing the d-axis current error and the q-axis current error by adopting a controller to obtain d-axis harmonic modulation voltage and q-axis harmonic modulation voltage;
carrying out dq/abc coordinate transformation on m-order harmonic waves on the d-axis harmonic wave modulation voltage and the q-axis harmonic wave modulation voltage to obtain harmonic wave modulation voltages of all phases under abc coordinates;
and summing the harmonic modulation voltages of each phase n to k, and then obtaining the harmonic modulation wave of each phase through an amplitude limiting link.
4. The method according to claim 3, further comprising an enable controller for controlling the modulated wave to be injected or extracted into the VSC, wherein the enable controller is disposed between summing and limiting the harmonic modulation voltages of each phase n-k.
5. The method according to claim 3, wherein the controller is a proportional-integral PI controller.
6. The method of suppressing hvdc transmission harmonics according to claim 3, wherein said controller is a proportional resonant PR controller.
7. The method according to claim 3, further comprising independently controlling harmonics of each order in a harmonic rejection stage using the harmonic modulation voltage of each phase.
8. The method according to claim 1, wherein the additional harmonic ac voltage of each phase is input to the flexible dc power transmission, and the flexible dc power transmission outputs a harmonic current of each phase current of 0.
9. The suppression system of the flexible direct current transmission harmonic waves is characterized by comprising a data acquisition unit, a processing unit, a conveying unit and a suppression unit;
the data acquisition unit is used for acquiring three-phase alternating current output by the converter in the flexible direct current transmission and three-phase alternating voltage of a grid-connected point of the converter in the flexible direct current transmission;
the processing unit is used for carrying out harmonic current control processing on the three-phase alternating current and the three-phase alternating voltage to generate three-phase harmonic modulation waves;
the transmission unit is used for inputting the three-phase harmonic modulation waves into a converter valve control system of the flexible direct-current transmission, and the converter outputs three-phase additional harmonic alternating-current voltages in the flexible direct-current transmission;
and the suppression unit is used for inputting the three-phase additional harmonic alternating-current voltage into the flexible direct-current transmission, and the harmonic current output in the flexible direct-current transmission is 0.
10. A computer device comprising a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the method for suppressing a hvdc transmission harmonic according to any of claims 1-8 according to instructions in the program code.
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